Leaking antifreeze
al i will throw another possible cause at you. i have a head gasket leak that leaks a little on the outside only of the engine. i can see it actually leave a little dried stain on the side of the block. only happens when hot then stopps when cold. if you can tell what side it is coming from look along the block near where the heads mate to it. you will see the dried stain there if it is doing it....